Electronic device for adjusting exposure value of image including face

Abstract

A method includes recognizing a face in a plurality of preview images. The method also includes setting a first exposure value of a first image such that a first brightness falls within a specified brightness range and the first brightness is of a first area including the face. The method further includes extracting a second brightness of an area excluding the first area. When the difference between the first brightness and the second brightness is greater than or equal to a specified value, the method includes adjusting exposure values of second and third images, which are a plurality of bracketing images having different exposures, as second and third exposure values, respectively. Additionally, the method includes synthesizing at least one of a bracketing image having a first exposure value, a second image, or a third image to generate a high dynamic range (HDR) image. The method includes displaying the HDR image.

What is claimed is: 
     
       1. An electronic device comprising:
 a housing including a first surface facing in a first direction and a second surface facing in a second direction opposite to the first surface; 
 a display exposed in the first direction through the first surface of the housing; 
 a camera at least partially exposed in the first direction through the first surface of the housing or at least partially exposed in the second direction through the second surface of the housing to photograph an image; and 
 a processor operatively coupled to the display and the camera, wherein the processor is configured to:
 recognize a face among a plurality of preview images, 
 set a first exposure value of a first image that is one of the plurality of preview images to a basic exposure value among the plurality of preview images such that a first brightness falls within a specified brightness range, wherein the first brightness is of a first area including the face, 
 extract the first brightness and a second brightness, wherein the second brightness is of a second area excluding the first area, 
 when a difference between the first brightness and the second brightness is greater than or equal to a specified difference value, adjust at least one of a second exposure value of a second image or a third exposure value of a third image, wherein the second image and the third image are bracketing images, wherein the second exposure value corresponding to the second image is smaller than the first exposure value of the first image, and wherein the third exposure value corresponding to the third image is greater than the first exposure value of the first image, 
 generate a high dynamic range (HDR) image by synthesizing at least one of a bracketing image including the first exposure value, the second image or the third image, and 
 display the generated high dynamic range image on the display. 
 
 
     
     
       2. The electronic device of  claim 1 , wherein the processor is further configured to:
 maintain the first exposure value and the third exposure value; and 
 adjust the second exposure value when the second brightness is brighter than the first brightness. 
 
     
     
       3. The electronic device of  claim 2 , wherein the processor is further configured to:
 set the second exposure value to a first correction value when a ratio of the second brightness to the first brightness is equal to or greater than a first boundary value; 
 set the second exposure value to a second correction value when the ratio is (i) less than the first boundary value and (ii) equal to or greater than a second boundary value, wherein the second correction value is greater than the first correction value and the second boundary value is less than the first boundary value; and 
 set the second exposure value to a third correction value when the ratio is (i) less than the second boundary value and (ii) equal to or greater than ‘1,’ wherein the third correction value that is (i) greater than the second correction value and (ii) less than the first exposure value. 
 
     
     
       4. The electronic device of  claim 2 , wherein the processor is further configured to:
 set the second exposure value to a first correction value when a ratio of the second brightness to the first brightness is equal to or greater than a first boundary value; 
 increase the second exposure value as the ratio decreases when the ratio is (i) less than the first boundary value and (ii) equal to or greater than a second boundary value, wherein the second boundary value is less than the first boundary value; and 
 set the second exposure value to a second correction value when the ratio is (i) less than the second boundary value and (ii) equal to or greater than ‘1,’ wherein the second correction value is (i) greater than the first correction value and (ii) less than the first exposure value. 
 
     
     
       5. The electronic device of  claim 1 , wherein the processor is further configured to:
 maintain the first exposure value and the second exposure value; and 
 adjust the third exposure value when the second brightness is darker than the first brightness. 
 
     
     
       6. The electronic device of  claim 5 , wherein the processor is further configured to:
 set the third exposure value to a first correction value when a ratio of the first brightness to the second brightness is equal to or greater than a first boundary value; 
 set the third exposure value to a second correction value when the ratio is (i) less than the first boundary value and (ii) equal to or greater than a second boundary value, wherein the second correction value smaller than the first correction value and the second boundary value is less than the first boundary value; and 
 set the third exposure value to a third correction value when the ratio is (i) less than the second boundary value and (ii) greater than ‘1,’ wherein the third correction value is (i) less than the second correction value and (ii) greater than the first exposure value. 
 
     
     
       7. The electronic device of  claim 5 , wherein the processor is further configured to:
 set the third exposure value as a first correction value when a ratio of the first brightness to the second brightness is equal to or greater than a first boundary value; 
 decrease the third exposure value as the ratio decreases when the ratio is (i) less than the first boundary value and (ii) equal to or greater than a second boundary value, wherein the second boundary value is less than the first boundary value; and 
 set the third exposure value as a third correction value that is less than a second correction value and greater than the first exposure value when the ratio is less than the second boundary value and greater than ‘1’. 
 
     
     
       8. The electronic device of  claim 1 , wherein the processor is further configured to:
 extract all brightness of the first area and the second area or extract brightness of a partial area in the second area including brightness outside a specified range to extract the second brightness. 
 
     
     
       9. A method of adjusting an exposure value of an image obtained by a camera of an electronic device including a display, the method comprising:
 recognizing a face among a plurality of preview images; 
 setting a first exposure value of a first image that is one of the plurality of preview images to a basic exposure value among the plurality of preview images such that a first brightness falls within a specified brightness range, wherein the first brightness is of a first area including the face; 
 extracting the first brightness and a second brightness, wherein the second brightness is of a second area excluding the first area; 
 when a difference between the first brightness and the second brightness is greater than or equal to a specified difference value, adjusting at least one of a second exposure value of a second image or a third exposure value of a third image, wherein the second image and the third image are bracketing images, wherein the second exposure value corresponding to the second image is smaller than the first exposure value of the first image, and wherein the third exposure value corresponding to the third image is greater than the first exposure value of the first image; 
 generating a high dynamic range image by synthesizing at least one of a bracketing image including the first exposure value, the second image or the third image; and 
 displaying the generated high dynamic range image on the display. 
 
     
     
       10. The method of  claim 9 , further comprising:
 maintaining the first exposure value and the third exposure value; and 
 adjusting the second exposure value when the second brightness is brighter than the first brightness. 
 
     
     
       11. The method of  claim 10 , further comprising:
 setting the second exposure value to a first correction value when a ratio of the second brightness to the first brightness is equal to or greater than a first boundary value; 
 setting the second exposure value to a second correction value when the ratio is (i) less than the first boundary value and (ii) equal to or greater than a second boundary value, wherein the second correction value is greater than the first correction value and the second boundary value is less than the first boundary value; and 
 setting the second exposure value to a third correction value when the ratio is (i) less than the second boundary value and (ii) equal to or greater than ‘1,’ wherein the third correction value that is (i) greater than the second correction value and (ii) less than the first exposure value. 
 
     
     
       12. The method of  claim 10 , further comprising:
 setting the second exposure value to a first correction value when a ratio of the second brightness to the first brightness is equal to or greater than a first boundary value; 
 increasing the second exposure value as the ratio decreases when the ratio is (i) less than the first boundary value and (ii) equal to or greater than a second boundary value, wherein the second boundary value is less than the first boundary value; and 
 setting the second exposure value to a second correction value when the ratio is (i) less than the second boundary value and (ii) equal to or greater than ‘1,’ wherein the second correction value is (i) greater than the first correction value and (ii) less than the first exposure value. 
 
     
     
       13. The method of  claim 9 , further comprising:
 maintaining the first exposure value and the second exposure value; and 
 adjusting the third exposure value when the second brightness is darker than the first brightness. 
 
     
     
       14. The method of  claim 13 , further comprising:
 setting the third exposure value to a first correction value when a ratio of the first brightness to the second brightness is equal to or greater than a first boundary value; 
 setting the third exposure value to a second correction value when the ratio is (i) less than the first boundary value and (ii) equal to or greater than a second boundary value, wherein the second correction value smaller than the first correction value and the second boundary value is less than the first boundary value; and 
 setting the third exposure value to a third correction value when the ratio is (i) less than the second boundary value and (ii) greater than ‘1,’ wherein the third correction value is (i) less than the second correction value and (ii) greater than the first exposure value. 
 
     
     
       15. The method of  claim 13 , further comprising:
 setting the third exposure value to a first correction value when a ratio of the first brightness to the second brightness is equal to or greater than a first boundary value; 
 decreasing the third exposure value as the ratio decreases when the ratio is (i) less than the first boundary value and (ii) equal to or greater than a second boundary value, wherein the second boundary value is less than the first boundary value; and 
 setting the third exposure value to a third correction value that is less than a second correction value and greater than the first exposure value when the ratio is less than the second boundary value and greater than ‘1’. 
 
     
     
       16. The method of  claim 9 , further comprising extracting all brightness of the first area and the second area or extract brightness of a partial area in the second area including brightness outside a specified range to extract the second brightness. 
     
     
       17. A non-transitory computer readable medium containing instructions that when executed cause at least one processor of an electronic device to:
 recognize a face among a plurality of preview images; 
 set a first exposure value of a first image that is one of the plurality of preview images to a basic exposure value among the plurality of preview images such that a first brightness falls within a specified brightness range, wherein the first brightness is of a first area including the face; 
 extract the first brightness and a second brightness, wherein the second brightness is of a second area excluding the first area; 
 when a difference between the first brightness and the second brightness is greater than or equal to a specified difference value, adjust at least one of a second exposure value of a second image or a third exposure value of a third image, wherein the second image and the third image are bracketing images, wherein the second exposure value corresponding to the second image is smaller than the first exposure value of the first image, and wherein the third exposure value corresponding to the third image is greater than the first exposure value of the first image; 
 generate a high dynamic range (HDR) image by synthesizing at least one of a bracketing image including the first exposure value, the second image or the third image; and 
 display the generated high dynamic range image on a display. 
 
     
     
       18. The computer readable medium of  claim 17 , further containing instructions that when executed cause the at least one processor to:
 maintain the first exposure value and the third exposure value; and 
 adjust the second exposure value when the second brightness is brighter than the first brightness. 
 
     
     
       19. The computer readable medium of  claim 18 , further containing instructions that when executed cause the at least one processor to:
 set the second exposure value to a first correction value when a ratio of the second brightness to the first brightness is equal to or greater than a first boundary value; 
 set the second exposure value to a second correction value when the ratio is (i) less than the first boundary value and (ii) equal to or greater than a second boundary value, wherein the second correction value is greater than the first correction value and the second boundary value is less than the first boundary value; and 
 set the second exposure value to a third correction value when the ratio is (i) less than the second boundary value and (ii) equal to or greater than ‘1,’ wherein the third correction value that is (i) greater than the second correction value and (ii) less than the first exposure value. 
 
     
     
       20. The computer readable medium of  claim 18 , further containing instructions that when executed cause the at least one processor to:
 set the second exposure value to a first correction value when a ratio of the second brightness to the first brightness is equal to or greater than a first boundary value; 
 increase the second exposure value as the ratio decreases when the ratio is (i) less than the first boundary value and (ii) equal to or greater than a second boundary value, wherein the second boundary value is less than the first boundary value; and 
 set the second exposure value to a second correction value when the ratio is (i) less than the second boundary value and (ii) equal to or greater than ‘1,’ wherein the second correction value is (i) greater than the first correction value and (ii) less than the first exposure value.